PrimeGrid’sCullen Prime Search
On 20 Apr 2009 0:52:45 UTC, PrimeGrid’s Cullen Prime Search found a world record
Cullen Mega Prime:6328548*26328548+1
The prime is PrimeGrid's largest to date. It is 1,905,090 digits long and will enter
Chris Caldwell's “The Largest Known Primes Database”(http://primes.utm.edu/primes) ranked 14th overall. It is the largest Cullen prime
found and the largest found Mega Prime using LLR.
The discovery was made by Dennis R. Gesker of the United States using an Intel
Xeon E5420 @ 2.50GHz with 8 GB RAM running Windows Server 2008. This
computer took about 32 hours 28 minutes to complete the primality test.
The prime was verified on 20 Apr 2009 16:24:29 UTC, by Jeff Morales of the UnitedStates using an Intel Pentium 4 @ 2.80GHz with 512 MB RAM running Windows XP
Professional. This computer took about 71 hours 55 minutes to complete theprimality test. Jeff is a member of the SETI.USA team.
The credits for the discovery are as follows:

1.
2.
3.
4.
5.

Dennis R. Gesker (United States), discoverer
PrimeGrid, et al.
MultiSieve, sieving program developed by Mark Rodenkirch
GCWsieve, sieving program developed by Geoff Reynolds
LLR, primality program developed by Jean Penné

Entry in “The Largest Know Primes Database” can be found here:
http://primes.utm.edu/primes/page.php?id=87775
This is only the 15th Cullen Prime found and PrimeGrid’s first. Cullen numbers werefirst studied by Reverend James Cullen in 1905. A Cullen prime is any prime of theform Cn=n*2^n+1. Cn is prime for n = 1, 141, 4713, 5795, 6611, 18496, 32292,32469, 59656, 90825, 262419, 361275, 481899, 1354828, 6328548.
Using a single PC would have taken years to find this prime. So this timely
discovery would not have been possible without the thousands of volunteers whocontributed their spare CPU cycles. A special thanks to everyone who contributed
their advice and/or computing power to the search - especially all the sievers whowork behind the scenes to make a find like this possible.
PrimeGrid’s Cullen Prime Search will continue to search for even larger primes. Tojoin the search please visit PrimeGrid: http://www.primegrid.com

PrimeGrid’sCullen Prime Search
About PrimeGrid
PrimeGrid is a distributed computing project, developed by Rytis Slatkevičius, whichutilizes BOINC and PRPNet to search for primes. PrimeGrid's primary goal is to bringthe excitement of prime finding to the "everyday" computer user. Simply download
the software and let your computer do the rest. Participants can choose from avariety of prime forms to search. With a little patience, you may find a large or evenrecord breaking prime.
BOINC
The Berkeley Open Infrastructure for Network Computing (BOINC) is asoftware platform for distributed computing using volunteered computerresources. It allows users to participate in multiple distributed computing
projects through a single program. Currently BOINC is being developed by ateam based at the University of California, Berkeley led by David Anderson.
This platform currently supports projects from biology to math to astronomy.
For more information, please visit BOINC: http://boinc.berkeley.edu
PRPNet
PRPNet is a distributed Client/Server application, developed by MarkRodenkirch, which can be used to manage and perform primality andprobable prime tests on a list of candidate numbers. The PRPNet Client usesLLR, Phrot, or PFGW to perform these tests.
For more information and a list of the all available prime search projects, please
visit PrimeGrid: http://www.primegrid.com